Velocity map imaging the dynamics of the reactions of Cl atoms with neopentane and tetramethylsilane

Abstract

The reactions of ground state Cl( 2 P 3/2 ) atoms with neopentane and tetramethylsilane have been studied at collision energies of 7.9 ± 2.0 and 8.2 ± 2.0 kcal mol -1 respectively. The nascent HCl(v=0, J) products were probed using REMPI spectroscopy combined with velocity map imaging (VMI) to determine rotational

Primary vs. secondary H-atom abstraction in the Cl-atom reaction with n-pentane

“…[7][8][9][10] The Cl-atom reactions with methane, ethane, larger alkanes and other organic compounds serve as model systems for the study of dynamics of gas-phase reactions of polyatomic molecules, [11][12][13] with detailed investigations performed in a number of laboratories. [14][15][16][17][18][19][20][21][22][23] Selected examples have also been the subjects of computer simulation using global potential energy surfaces 10,24 or direct dynamics calculations, [25][26][27] with calculated product quantum state populations and state-resolved differential cross sections that are in reasonable accord with experimental data. A combination of the experimental and computational outcomes has highlighted the importance of weak interactions in the post-transition state (TS) region in determining product quantum state distributions.…”

“…41 This rate coefficient is an average over reaction sites, but the energy released depends on whether a primary or secondary H atom is abstracted: 42 Cl + n-pentane  HCl + 1-pentyl rH = 8.4 kJ mol The reactions of Cl with ethane and neopentane, in which only a primary H-atom is available for removal, have reaction enthalpy changes of rH = 8.7  1.6 and 10.5  8.4 kJ mol -1 respectively that are comparable to reaction (1a). 23,43 The location of primary H atoms at the periphery of an n-pentane molecule favours their abstraction in large impact-parameter collisions with Cl atoms, whereas the greater energy release for reaction (1b) instead might promote secondary H-atom abstraction by moving the TS earlier along the reaction coordinate. The current study examines the product energy disposal for signatures of the different thermochemistries of reactions (1a) and (1b) in the reaction dynamics, and analyses angular scattering distributions for evidence of the preferred impact parameters for reaction.…”

Direct and Indirect Hydrogen Abstraction in Cl + Alkene Reactions

“…[23][24] Two independently controlled pulsed valves form parallel molecular beams in a vacuum chamber, as shown in Figure photolysis laser on or off every 50 probe laser pulses to record instrument background. We present only images using this background subtraction.…”

Vibrationally resolved dynamics of the reaction of Cl atoms with 2,3-dimethylbut-2-ene in chlorinated solvents

“…1, 2 Direct abstraction of an H atom is observed for reactions of Cl atoms with alkanes, [3][4][5] whereas reactions with alkenes show competition between direct abstraction and addition-elimination pathways. [6][7][8] Reactions of Cl atoms with simple alcohols, amines, haloalkanes and ethers exhibit similar abstraction dynamics, [9][10][11][12][13][14][15] with further interaction of the separating products after the transition state (TS) also influencing the scattering.…”